The Knox County, Tenn., school system was among the first to adopt block scheduling in 1993. Donna Wright, now an assistant superintendent of curriculum and instruction there, said she became interested in the format when she and other principals were looking for a way to expand schedules to help students meet lengthier graduation requirements. Each student needed eight classes a year to make room for required courses and interesting electives. But there was no room for eight periods a day. Having four periods a day, alternating every other day or every semester, seemed the way to go.

"A lecture over 90 minutes can be pretty deadly, however," she said. She and other educators have since been looking for ways to train teachers and organize time better. She said she sees no major backlash against block scheduling, but there have been complaints.

In Washington area public high schools, block schedules are the norm in the District, most of Northern Virginia and in Anne Arundel, Carroll, Frederick and Prince George's counties. Traditional schedules prevail in Howard, Calvert and St. Mary's counties.

Stafford, Montgomery and Charles counties have some of both.

David A. Bruzga, administrative director for Howard secondary schools, said officials there decided to go back to a traditional system in 2003 after struggling with five block systems. A committee studying the situation decided a uniform scheduling format would make it easier for students if they transferred schools. It was difficult to schedule Advanced Placement classes in some block systems. The lack of much research showing achievement gains from block scheduling also influenced the choice, he said.

Stephen L. Bedford, chief school performance officer in Montgomery, said the county's schools were allowed to decide for themselves, particularly after "we looked at the national research and it was very sketchy as to which schedule worked better than another." Montgomery high schools with some form of block scheduling are Montgomery Blair, James Hubert Blake, Northwood, Springbrook and Wheaton.

Northwood Principal Henry Johnson said he made clear to all teachers he hired for the new school in 2004 that they would have a block schedule, so faculty support was strong. School system officials objected to the original plan for four courses a semester, so he switched to four courses alternating daily and found that it worked well. But there is some dissent, he said. When the faculty voted last year on whether to stay on the block schedule, there were nearly as many votes against it as for it.

Several educators said they do not expect a rapid abandonment of block scheduling but more experiments mixing block and traditional. "What we are doing is trying to impact student learning in a way that meets the individual learning needs of students," Wright said, "as opposed to looking at what is convenient for teachers."

At Einstein, Fernandez said, so far the traditional schedule "seems to be working. I think we are getting better attendance."